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Total newbie question but what is the best practice when it comes to using SSH with Git? I'm working on a WordPress project. In the root I have gulp and other dev files/folders like SASS and Scripts that I don't need on the server and in the same project I have my WordPress folder that contains a theme and a few custom plugins. As you can imagine when the theme or any of the plugins are ready to be deployed I don't want to pull everything in my repository on the server. So far as a newbie I've always just pull and pushed the entire repository and used FTP to upload what I need to the server, so how is this done with SSH and Git and is there a better way to have my setup?
EDIT: To make my question a little bit more clear let me give you an example of what I think my issue is. In my main project folder, I have a SASS folder next to my WordPress folder. All I really need to deploy to the server is the WordPress folder. My build process that happens on my dev machine combines all of the SASS files into a single CSS that is then placed into the WordPress folder. I need the SASS folder to be tracked by Git so that any other developer can pull them and continue developing so I can't have git ignore it. However none of those SASS files need to be on the server for WordPress to work either. I just simply need to deploy the WordPress folder and everything that's in it.
I understand the idea of creating a bare repository on the server and using post-receive hook to point the git folder sitting outside your web root to point to where the web root is. But that's basically how GIT and SSH work and that's not answering my concern.
Not with Git
Git is not designed to pull specific files or directories only. It's a directed acyclic graph with binary blobs as objects and sometimes multiple objects get compacted into a single larger object.
Due to Git design, your specific request is not possible.
Alternatives
post-receive hook
If your website only contains simple static files then it's okay to push to a git repository over SSH. In reality, it's unlikely your repository will be large as long as you don't have non-text files.
Take for example the following setup.
/var/lib/www - apache web dir which is the cloned copy of www.git
/var/lib/www.git - a bare git repository.
/var/lib/www.git/hooks/post-recieve - A server side git hook. It can be a shell script that pulls the www repository when this repository is updated.
Sample post-recieve hook script:
#!/bin/bash
cd /home/sam/sandbox/git-hooks/www
unset GIT_DIR
git fetch origin master
git reset --hard origin/master
Zip up build in a tar.gz
At the end of your build you can zip up your files in a tar.gz. This file should be hosted somewhere (perhaps GitHub releases if you're using GitHub). Some enterprises use on premise artifact hosting like Nexus or Artifactory.
The idea being: you have a tested artifact that has a specific sha256sum. The artifact you test is the exact same artifact which eventually goes to production.
Diving into more detail such as continuous integration, continuous delivery, and the software development life cycle might be out of scope for your question.
No best practice.
Git is for source control, not for deployment. There is no best practice for using git this way because git is not a deployment tool. You also don't need git history on your server. In fact, you don't need git at all unless you insist on using it for deployment. You are welcome to use it this way but it's not ideal because of exactly the kind of problem you're asking about.
What is the best practice?
There are a number of tools you could use to handle your deployments. Most of the tools generally let you set up a series of steps that let you deploy the code you want into the environment you want. You could go with simple tools such as Phing or Deployer in the PHP world, or something more sophisticated like Puppet or Chef if you have more complex needs. You could just write your own bash scripts if what you need is really very simple. I recommend Phing or Deployer given the info you've provided. https://deployer.org/ https://www.phing.info/
You'll just configure whichever tool you want to ssh into your target box and copy over only the files you want into the directory you want on the server, in whatever way you would like to do that. Usually, you have the script copy files into a temp dir, tarball them up, ssh them over and untar them. After that, you'll usually do some additional work on the server to move files around, change symlinks, whatever else you might need to do.
What about compiled SASS, ES6 js files, or modern static stuff?
All you need to do is add steps to the handle the static files and where you want them to go. Include the generated static files in your tarball when you push stuff up, and put them in the right directories in the server once you untar it.
When you configured your SASS compiler, and whatever other pre-compiled static code you may have - you configured it to create a destination file. That is, the file(s) of actual CSS and JS that they generate. That's all you need to bring along - and if you have the destination directory set to be inside your wordpress theme, you may not even have to pay all that much special attention to it's handling. You may need to move them somewhere else once they are on the server but that all depends on the specific setup in your server, which I think is outside the scope of this question.
Additional Notes:
You didn't ask about this but I thought it was worth mentioning, that you shouldn't be sending the entire wordpress repository every time you update. Just like you don't need the uncompiled SASS code, you also don't need to be repackaging core WordPress. You don't even need to be commiting core WordPress, its a dependency and you don't need to be changing it.
All that should be getting committed by you is your theme and plugin code, and the uncompiled static files. Compiled static files and external dependencies like the WordPress core don't belong in your git history. For deployment purposes, WordPress should already be installed. The stuff in your tarballs should just be plugins and themes, and additional static files if they aren't already in there for some reason.
TLDR;
Don't use git for this. Use a tool like Phing or Deployer. Build your static files into your theme, and create phing/deployer scripts that tarball up only the code you want, SSH's it over to your server, and untars it into the directories you want. If you have some special location on the server for your static files, just make sure to add steps in your script for that.
So, based on your question and comment, there are three computers involved. There is a web server (when you say "server", I take it as a Web server in this scenario, or the server computer that runs a Web server program). There is another server where your git repo is hosted. And, there is your dev workstation. Is this correct?
It seems like, you have a cloned git repo on your Web server. Your current practice/workflow appears to be (1) (based on your expression "SSH'ed into my server") you log into the web server via SSH (just like Telnet) from your workstation (SSH is just a protocol, which can be used for different purposes). (2) you pull from your repo on hosted service (e.g., github), and (3) deploy it to your "www" directory on the same server. Is this correct?
(I can think of an alternative scenario based on your use of the word "FTP", etc., but let's focus on the above scenario, for now.)
Now, your question is, whenever you "pull" (on your Web server), you feel like you are pulling everything from your repo on your hosted service. And, is there a better way? Am I understanding your question correctly?
If so, as another commenter suggested, git (and, any version control system, in general) is very good at fetching "deltas" only. If you are worried about "fetching everything" every time you pull (the step (2) above), then your worry is unfounded.
Now, the question is, why do you have a git repo on your Web server, if that is indeed the case? This is a pretty legit setup and I've done this before (e.g., on EC2). But, as a best practice, people generally don't do that on "production" servers. It's because you have to "build" your web app, and you really don't want to do that on production servers.
The next question is, what do you exactly do in Step (3)? The build process (whatever process you use) typically generates an "output" which can be directly deployed to the web server. (The convention is the output is generally a single folder, "public", "www", "dist", or whatever, or a single file (e.g., tar.gz, zip, jar, war), etc.) Regardless of whether you build the deployable output on your dev workstation (or, a build machine) or on your Web server, you don't generally do "deltas" in this context. Even if you've only changed a single file (say, a CSS file), you generally build the whole output again (instead of, say, just replacing the changed CSS file only). When you use FTP to upload files, etc., you can selectively upload certain files and/or directories, etc., but as a general practice, we don't do that. We always build the complete output from scratch and deploy it to the Web server. (This is mainly to reduce the potential deployment errors and increase the reliability.)
So, to answer your question, (A) If you are pulling git repo on your Web server, you should really change that practice, and move the build process to your dev computer or a dedicated build machine. (BTW, services like github, gitlab, TFS, ... provide the build service for you.) (B) If you are currently selectively FTP'ing your web app files to your Web server, then you should really consider adopting some kind of formal build, and deployment, process moving forward.
After your SASS build process is done use scp or rsync to move the files to the prod server:
scp -r /[local wordpress dir]/wp-content/themes/your-theme/ username#your.prod.server.com:/path/to/dir/wordpress/wp-content/themes/
scp -r /[local wordpress dir]/wp-content/plugins/* username#your.prod.server.com:/path/to/dir/wordpress/wp-content/plugins/
I am working in a project and using git ssh with bitbucket following is the process i am using it may work for you also if not please correct me :
Step 1 ->I have setup git and create repo in bit-bucket.
Step 2 ->And setup project with my local and linked with my repo.
Step 3 ->connect my server using ssh.
Step 4 ->Work in my local and commit and push all changes in my git repo.
Step 5 ->Run git pull on ssh so all changes deployed in my server.
I am using above process and i love this process.i have used .gitignore file that is not required for push on my repo.
Thanks
Is there any way in ASP.NET website project, that allow to publish it from command prompt and I can continue working on project, or if it is not easy to use , at least speed up my publish task?
I know about the auto publishing tools like TFS or CruiseControl, so please don't tell me these ways.
I am thinking to create a .bat file , that I'll run everytime I have to publish. but it should not take changes made by me during its running process.
asp.net single file publish
I really like the Answer given by Ludwo, providing more information on that would be very helpful.
You can use MsBuild to publish your websites in parallel. Start with this article. It is about publishing one website using MsBuild. Define your projects inside ItemGroup and use MSBuild task this way:
<MSBuild Projects="#(YourProjectsToBuildInParallel)" BuildInParallel="true" ...
The final step is to enable parallel processing for MSBuild task.
Open another Visual Studio to continue :P. Publishing mechanism can detect updated and can send only changes. So dont upload full site everytime, if its really disturbs you.
Use source control and a build server mechanism. The build server should be able to pull from source control when you commit a change, build the project, do any unit tests you may/should have, and then deploy to a test site.
Depending on which build server platform you use you may or may have to do varying amounts of work. In the past I have used Bamboo by Atlassian. Fantastic product but you have to configure the deployment using MSBuild - it's fine but it can take some time to get it perfect. I am sure there are some good examples out there for it.
How it will work for you:
When you are finished working on a file/issue you can commit your changes. The build server will then detect these changes and wait a varying amount of time (waiting for you to commit more) e.g. 3 minutes, check out your changes, and deploy. You can set up notifications when the deployment is done to goto your testing team - with a link in the email saying where the site is, and what the change that occurred (based on your SVN commit log).
So your net effort is to check a file in with a correct comment - and you are finished.
Here is what I am trying to do: I have my code sitting on Bitbucket (it is a ASP.net web application). I want to put together a build machine that has a web-based dashboard. I go to the dashboard and I say: Ok show me all the branches and stuff on my Bitbucket project. Now please get the latest code from this branch for me and build it. Then please deploy it to this location for me or maybe this other location. I want this dashboard give me a history of all this builds and deployments too. I am very new to this concept I have been reading about CC.net and MSBuild and other stuff but I can not find the right answer. Please put me in the right direction.
The point of a build server is that it automatically runs a build each time you commit something to your repository.
In order for the build server to know exactly what to do, you normally put a build script (with MSBuild or NAnt) into your solution which does everything you want - building your solution, maybe create a setup package and so on.
The build server basically knows where the repository is and where in the repository your build script is.
You need to configure this once in the build server, and then it will always run after you commit (but you can also start a build manually, if you want).
If you want a solution with web-based dashboard, try TeamCity.
It's a commercial product, but it's free for up to 20 users.
You can do everything in the web interface - configuration, running the builds AND browsing the build history.
EDIT:
Houda, concerning your question about deployment:
I don't think that TeamCity has a "deployment mode" in that sense. What you could do is include the deployment stuff in your build script that is run by TeamCity.
So, after the build itself is finished, copy the generated assemblies and files on your web server(s).
If you do it this way, you HAVE to make sure in the build script that the deployment will only happen if the build didn't fail (and if you have unit tests, if the unit tests didn't fail as well).
This is very important for a live application, because if you don't take care of this well enough, your app will go immediately offline every time someone commits "bad" code to your repository (and it will stay offline until the next "good" commit)!!
EDIT 2:
See Lasse V. Karlsen's comment below: it's more comfortable with the new TeamCity version 6.
I need to deploy a website from the SVN to different servers all within our own network. The code is currently not compiled but probably will be in the future.
First, the site would need to be deployed to the development server for the developers to test.
Once the Developer signs off, it would be deployed to the staging server for the testers.
Once final sign off was given it would be deployed to a server farm- two live servers.
Each server has a couple of settings in the web.config to that are different (except the two live servers, of course). I would like to use templates, the way the Ruby on Rails world does. It seems like an elegant solution to multiple web.config files.
I also need to create a list/report of the files that were changed and what the change was since the last deployment.
I am thinking of writing a script that will do the following:
1. Take args for server to deploy to, and revision
2. Export a copy of the source to a directory with svn export -r <deploy revision>
3. Delete the web.config file
4. Use ttree (a template tool http://template-toolkit.org/) to create the correct web.config
5. Create a list of file changes with svn list -r <deploy revision>:<current server revision>
6. Store the <current server revision> of the website for when the script is run next time
The problem I have is it doesn't seem like the most elegant solution. It could become unmaintainable, and I prefer to use tools that are already available rather than re-invent the wheel. Unfortunately I don't think MSDeploy will do what I need, but I'm happy to use it, or anything else, if it will do what I need it to. Does anyone know of any tools that are up to the task or is the script my only option?
Check out TeamCity. I have my build server setup so that it can deploy to different environments with different settings based on the build configuration all in "One Click". It's relatively painless to setup and integrates directly with Subversion and other source control systems. This would be a more elegant solution to the issue you are dealing with...
I am looking for different techniques/tools you use to deploy an ASP.NET web application project (NOT ASP.NET web site) to production?
I am particularly interested of the workflow happening between the time your Continuous Integration Build server drops the binaries at some location and the time the first user request hits these binaries.
Are you using some specific tools or just XCOPY? How is the application packaged (ZIP, MSI, ...)?
When an application is deployed for the first time how do you setup the App Pool and Virtual Directory (do you create them manually or with some tool)?
When a static resource changes (CSS, JS or image file) do you redeploy the whole application or only the modified resource? How about when an assembly/ASPX page changes?
Do you keep track of all deployed versions for a given application and in case something goes wrong do you have procedures of restoring the application to a previous known working state?
Feel free to complete the previous list.
And here's what we use to deploy our ASP.NET applications:
We add a Web Deployment Project to the solution and set it up to build the ASP.NET web application
We add a Setup Project (NOT Web Setup Project) to the solution and set it to take the output of the Web Deployment Project
We add a custom install action and in the OnInstall event we run a custom build .NET assembly that creates an App Pool and a Virtual Directory in IIS using System.DirectoryServices.DirectoryEntry (This task is performed only the first time an application is deployed). We support multiple Web Sites in IIS, Authentication for Virtual Directories and setting identities for App Pools.
We add a custom task in TFS to build the Setup Project (TFS does not support Setup Projects so we had to use devenv.exe to build the MSI)
The MSI is installed on the live server (if there's a previous version of the MSI it is first uninstalled)
We have all of our code deployed in MSIs using Setup Factory. If something has to change we redeploy the entire solution. This sounds like overkill for a css file, but it absolutely keeps all environments in sync, and we know exactly what is in production (we deploy to all test and uat environments the same way).
We do rolling deployment to the live servers, so we don't use installer projects; we have something more like CI:
"live" build-server builds from the approved source (not the "HEAD" of the repo)
(after it has taken a backup ;-p)
robocopy publishes to a staging server ("live", but not in the F5 cluster)
final validation done on the staging server, often with "hosts" hacks to emulate the entire thing as closely as possible
robocopy /L is used automatically to distribute a list of the changes in the next "push", to alert of any goofs
as part of a scheduled process, the cluster is cycled, deploying to the nodes in the cluster via robocopy (while they are out of the cluster)
robocopy automatically ensures that only changes are deployed.
Re the App Pool etc; I would love this to be automated (see this question), but at the moment it is manual. I really want to change that, though.
(it probably helps that we have our own data-centre and server-farm "on-site", so we don't have to cross many hurdles)
Website
Deployer:
http://www.codeproject.com/KB/install/deployer.aspx
I publish website to a local folder, zip it, then upload it over FTP. Deployer on server then extracts zip, replaces config values (in Web.Config and other files), and that's it.
Of course for first run you need to connect to the server and setup IIS WebSite, database, but after that publishing updates is piece of cake.
Database
For keeping databases in sync I use http://www.red-gate.com/products/sql-development/sql-compare/
If server is behind bunch of routers and you can't directly connect (which is requirement of SQL Compare), use https://secure.logmein.com/products/hamachi2/ to create VPN.
I deploy mostly ASP.NET apps to Linux servers and redeploy everything for even the smallest change. Here is my standard workflow:
I use a source code repository (like Subversion)
On the server, I have a bash script that does the following:
Checks out the latest code
Does a build (creates the DLLs)
Filters the files down to the essentials (removes code files for example)
Backs up the database
Deploys the files to the web server in a directory named with the current date
Updates the database if a new schema is included in the deployment
Makes the new installation the default one so it will be served with the next hit
Checkout is done with the command-line version of Subversion and building is done with xbuild (msbuild work-alike from the Mono project). Most of the magic is done in ReleaseIt.
On my dev server I essentially have continuous integration but on the production side I actually SSH into the server and initiate the deployment manually by running the script. My script is cleverly called 'deploy' so that is what I type at the bash prompt. I am very creative. Not.
In production, I have to type 'deploy' twice: once to check-out, build, and deploy to a dated directory and once to make that directory the default instance. Since the directories are dated, I can revert to any previous deployment simply by typing 'deploy' from within the relevant directory.
Initial deployment takes a couple of minutes and reversion to a prior version takes a few seconds.
It has been a nice solution for me and relies only on the three command-line utilities (svn, xbuild, and releaseit), the DB client, SSH, and Bash.
I really need to update the copy of ReleaseIt on CodePlex sometime:
http://releaseit.codeplex.com/
Simple XCopy for ASP.NET. Zip it up, sftp to the server, extract into the right location. For the first deployment, manual set up of IIS
Answering your questions:
XCopy
Manually
For static resources, we only deploy the changed resource.
For DLL's we deploy the changed DLL and ASPX pages.
Yes, and yes.
Keeping it nice and simple has saved us alot of headaches so far.
Are you using some specific tools or just XCOPY? How is the application packaged (ZIP, MSI, ...)?
As a developer for BuildMaster, this is naturally what I use. All applications are built and packaged within the tool as artifacts, which are stored internally as ZIP files.
When an application is deployed for the first time how do you setup the App Pool and Virtual Directory (do you create them manually or with some tool)?
Manually - we create a change control within the tool that reminds us the exact steps to perform in future environments as the application moves through its testing environments. This could also be automated with a simple PowerShell script, but we do not add new applications very often so it's just as easy to spend the 1 minute it takes to create the site manually.
When a static resource changes (CSS, JS or image file) do you redeploy the whole application or only the modified resource? How about when an assembly/ASPX page changes?
By default, the process of deploying artifacts is set-up such that only files that are modified are transferred to the target server - this includes everything from CSS files, JavaScript files, ASPX pages, and linked assemblies.
Do you keep track of all deployed versions for a given application and in case something goes wrong do you have procedures of restoring the application to a previous known working state?
Yes, BuildMaster handles all of this for us. Restoring is mostly as simple as re-executing an old build promotion, but sometimes database changes need to be manually restored, and data loss can occur. The basic rollback process is detailed here: http://inedo.com/support/tutorials/performing-a-deployment-rollback-with-buildmaster
web setup/install projects - so you can easily uninstall it if something goes wrong
Unfold is a capistrano-like deployment solution I wrote for .net applications. It is what we use on all of our projects and it's a very flexible solution. It solves most of the typical problems for .net applications as explained in this blog post by Rob Conery.
it comes with a good "default" behavior, in the sense that it does a lot of standard stuff for you: getting the code from source control, building, creating the application pool, setting up IIS, etc
releases based on what's in source control
it has task hooks, so the default behaviour can be easily extended or altered
it has rollback
it's all powershell, so there aren't any external dependencies
it uses powershell remoting to access remote machines
Here's an introduction and some other blog posts.
So to answer the questions above:
How is the application packaged (ZIP, MSI, ...)?
Git (or another scm) is the default way to get the application on the target machine. Alternatively you can perform a local build and copy the result over the Powereshell remoting connection
When an application is deployed for the first time how do you setup the App Pool and Virtual Directory (do you create them manually or with some tool)?
Unfold configures the application pool and website application using Powershell's WebAdministration Module. It allows us (and you) to modify any aspect of the application pool or website
When a static resource changes (CSS, JS or image file) do you redeploy the whole application or only the modified resource? How about when an assembly/ASPX page changes?
Yes unfold does this, any deploy is installed next to the others. That way we can easily rollback
when somehting goes wrong. It also allows us to easily trace back a deployed version to
a source control revision.
Do you keep track of all deployed versions for a given application?
Yes, unfold keeps old versions around. Not all versions, but a number of versions. It makes rolling back almost trivial.
We've been improving our release process for the past year and now we've got it down pat. I'm using Jenkins to manage all of our automated builds and releases, but I'm sure you could use TeamCity or CruiseControl.
So upon checkin, our "normal" build does the following:
Jenkins does a SVN update to fetch the latest version of the code
A NuGet package restore is done running against our own local NuGet repository
The application is compiled using MsBuild. Setting this up is an adventure, because you need to install the correct MsBuild and then the ASP.NET and MVC dll's on your build box. (As a side note, when I had <MvcBuildViews>true</MvcBuildViews> entered in my .csproj files to compile the views, msbuild was randomly crashing, so I had to disable it)
Once the code is compiled the unit tests are run (I'm using nunit for this, but you can use anything you want)
If all the unit tests pass, I stop the IIS app pool, deploy the app locally (just a few basic XCOPY commands to copy over the necessary files) and then restart IIS (I've had problems with IIS locking files, and this solved it)
I have separate web.config files for each environment; dev, uat, prod. (I tried using the web transformation stuff with little success). So the right web.config file is also copied across
I then use PhantomJS to execute a bunch of UI tests. It also takes a bunch of screenshots at different resolutions (mobile, desktop) and stamps each screenshot with some information (page title, resolution). Jenkins has great support for handling these screenshots and they are saved as part of the build
Once the integration UI tests pass the build is successful
If someone clicks "Deploy to UAT":
If the last build was successful, Jenkins does another SVN update
The application is compiled using a RELEASE configuration
A "www" directory is created and the application is copied into it
I then use winscp to synchronise the filesystem between the build box and UAT
I send a HTTP request to the UAT server and make sure I get back a 200
This revision is tagged in SVN as UAT-datetime
If we've got this far, build is successful!
When we click "Deploy to Prod":
The user selects a UAT Tag that was previously created
The tag is "switched" to
Code is compiled and synced with Prod server
Http request to Prod server
This revision is tagged in SVN as Prod-datetime
The release is zipped and stored
All up a full build to production takes about 30 secs which I'm very, very happy with.
Upsides to this solution:
It's fast
Unit tests should catch logic errors
When a UI bug gets into production, the screenshots will hopefully show what revision # caused the it
UAT and Prod are kept in sync
Jenkins shows you a great release history to UAT and Prod with all of the commit messages
UAT and Prod releases are all tagged automatically
You can see when releases happen and who did them
The main downsides to this solution are:
Whenever you do a release to Prod you need to do a release to UAT. This was a conscious decision we made because we wanted to always ensure that UAT is always up to date with Prod. Still, it's a pain.
There's quite a few configuration files floating around. I've attempted to have it all in Jenkins, but there's a few support batch files needed as part of the process. (These are also checked in).
DB upgrade and downgrade scripts are part of the app and run at app startup. It works (mostly), but it's a pain.
I'd love to hear any other possible improvements!
Back in 2009, where this answer hails from, we used CruiseControl.net for our Continuous Integration builds, which also outputted Release Media.
From there we used Smart Sync software to compare against a production server that was out of the load balanced pool, and moved the changes up.
Finally, after validating the release, we ran a DOS script that primarily used RoboCopy to sync the code over to the live servers, stopping/starting IIS as it went.
At the last company I worked for we used to deploy using an rSync batch file to upload only the changes since the last upload. The beauty of rSync is that you can add exclude lists to exclude specific files or filename patterns. So excluding all of our .cs files, solution and project files is really easy, for instance.
We were using TortoiseSVN for version control, and so it was nice to be able to write in several SVN commands to accomplish the following:
First off, check the user has the latest revision. If not, either prompt them to update or run the update right there and then.
Download a text file from the server called "synclog.txt" that details who the SVN user is, what revision number they are uploading and the date and time of the upload. Append a new line for the current upload and then send it back to the server along with the changed files. This makes it extremely easy to find out what version of the site to roll back to on the off chance that an upload causes problems.
In addition to this there is a second batch file that just checks for file differences on the live server. This can highlight the common problem where someone would upload but not commit their changes to SVN. Combined with the sync log mentioned above we could find out who the likely culprit was and ask them to commit their work.
And lastly, rSync allows you to take a backup of the files that were replaced during the upload. We had it move them into a backup folder So if you suddenly realised that some of the files should not have been overwritten, you can find the last backup up version of every file in that folder.
While the solution felt a little clunky at the time I have since come to appreciate it a whole lot more when working in environments where the upload method is a lot less elegant or easy (remote desktop, copy and paste the entire site, for instance).
I'd recommend NOT just overwriting existing application files but instead create a directory per version and repointing the IIS application to the new path.
This has several benefits:
Quick to revert if needed
No need to stop IIS or the app pool to avoid locking issues
No risk of old files causing problems
More or less zero downtime (usually just a pause at the new appdomain initialises)
The only issue we've had is resources being cached if you don't restart the app pool and rely on the automatic appdomain switch.